Thin film magnetic head with magnetically insulating layer for suppressing undershoots

ABSTRACT

A thin film magnetic head has first and second magnetic pole layers and, a thin film coil, a magnetic gap layer, and a magnetically insulating layer. The magnetically insulating layer is disposed along a plane facing a recording medium, and divides at least one of the front end section of the first magnetic pole layer and the frond end section of the second magnetic pole layer into a plurality of sub-sections. An additional magnetic pole layer may be provided on at least one of the front end section of the first magnetic pole layer and the front end section of the second magnetic pole layer with a magnetically insulating layer being interposed therebetween, The thin film magnetic head thus fabricated enables the reduction of undershoots to appear at both sides of a main peak of the waveform a signal reproduced by the magnetic head.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a thin film magnetic head to be used in amagnetic recording device, and more particularly to a thin film magnetichead with an improved reliability achieved by reducing to a lower levelthe magnitude of "undershoot" that appears on both sides of a main peakof the waveform of the reproduced data signal.

(2) Description of the Related Art

A magnetic recording device comprises as essential components thereof amagnetic recording medium for storing data that is mainly made of a hardmagnetic thin film and a magnetic head for recording data into andreproducing them from the magnetic recording medium. Because of therecent technological development for high density data storage, the thinfilm magnetic head has been remarkably improved in terms of not onlydata recording density but also the data recording frequency. Currently,thin film magnetic heads having a low inductance and a high signalreproducing efficiency are generally used to realize a high datarecording density. A thin film magnetic head comprises a pair ofmagnetic poles with a gap disposed therebetween, which magnetic polesare made of respective thin films having a thickness of severalmicrometers.

A first known thin film magnetic head is shown in FIGS. 1A and 1B of theaccompanying drawings, of which FIG. 1A illustrates a schematicsectional view of the head, and FIG. 1B illustrates an output waveformof a reproduced signal.

As shown, in this known thin film magnetic head comprises first andsecond magnetic pole layers 100 and 102 that are connected to each otherat the respective base sections 100d and 102d and are made of thin filmsoft magnetic materials, a thin film coil 103 wound at least aroundeither the first magnetic pole layer 100 or the second magnetic polelayer 102 and a magnetic gap layer 104 disposed between the front endsections 100a and 102a of the first and second magnetic pole layers 100and 102.

As shown, an isolated transition of magnetization 112 is formed toseparate opposite magnetizing directions 108 and 110 of a recordingmedium 106 disposed under the magnetic head. When the recording mediummoves along arrow 113, the data signal reproduced by the thin filmmagnetic head shows a waveform having an isolated main peak 114representing the reproduced data signal and two undershoots 116 locatedrespectively on lateral sides of the main peak 114 and producedrespectively corresponding to a lateral section 100b of the firstmagnetic pole layer 100 and a lateral section 102b of the secondmagnetic pole layer 102.

The undershoot output 116 located on the respective lateral sides of theisolated main peak 114 have a polarity opposite to that of the isolatedmain peak 114 and interferes with the isolated main peak 114 to changethe value of the isolated main peak 114 as the recording linear densityof the recording medium increases and the distance separated by theisolated transition of magnetization 112 is reduced. Additionally, theisolated main peak 114 can eventually be caused to be shifted.

The undershoot outputs 116 appear when the isolated transition ofmagnetization 112 of the recording medium 106 passes by the lateralsection 100b and goes under the first magnetic pole layer 100 and whenit passes by the lateral section 102b and leaves the second magneticpole layer 102, and this is because the rate at which the magnetic fluxgenerated by the isolated transition of magnetization 112 flows into thefirst magnetic pole layer 100 and the second magnetic pole layer 102changes abruptly at those respective points.

A second known thin film magnetic head is proposed in IEEE Transactionson Magnetics, Vol. 29, No. 6., pp. 3837-3839 (November 1993) to reducethe undershoots 116 having the polarity opposite to that of the isolatedmain peak 114. FIGS. 2A and 2B of the accompanying drawings illustratethe proposed magnetic head. FIG. 2A shows an enlarged schematic partialsectional view of the head and FIG. 2B shows the output waveform of areproduced signal. Here, the components that are same or similar totheir counterparts of the magnetic head of FIGS. 1A and 1B are denotedrespectively by the same reference symbols.

The second known thin film magnetic head is provided on the front endsections 100a and 102a of the first and second magnetic pole layers 100and 102 with recesses 100c and 102c. These recesses 100c and 102c areformed by partly removing the respective front end sections 100a and102a by means of an appropriate technique such as ion etching or ionmilling. As a result, the undershoots 118 have an amplitude slightlysmaller than that of the undershoots of the first known magnetic head.

However, the above described second known thin film magnetic head isaccompanied by the following problems.

(1) While the undershoot outputs 118 have a low profile, they are stillthere. As described above, the undershoots result in shifting of theisolated main peak and hence raising the detection error rate in thepeak detecting operation conducted when the magnetic recording device isoperating for data reproduction.

(2) As the front end sections 100a and 102a are partly removed, they aremade partly very thin on the respective sides of the magnetic gap 104.Then, a magnetically saturated state appears in the front end sections100a and 102a when an electric current flows therethrough for datarecording operation so that the transition of magnetization 112 isbroadened resulting in the reduction of the output level for highdensity data recording.

(3) Because of the recessed profile of the front end sections 100c and102c, dust and other contaminants can easily be caught there toconsequently reduce the reliability of the magnetic recording devicecomprising such a thin film magnetic head.

(4) In order to form recesses in the front end sections 100a and 102a,their forming process must be carried out from the side that is to bemagnetically floated. More specifically, after slicing a wafer into rowsto be worked with a slider for preparing thin film magnetic heads, eachof the rows is exposed to light and subjected to an intricate processingoperation typically involving ion milling to produce recesses 100c and102c. Thus, wafers cannot be treated on a mass production basis and theproductivity of preparing such recesses is inevitably low.

SUMMARY OF THE INVENTION

A object of the present invention, therefore, is to overcome theproblems existing in the prior art, and to provide a thin film magnetichead and a fabrication process therefor, which enables the reduction ofthe magnitude of undershoots appearing on the lateral sides of the mainpeak of the waveform of the reproduced data signal to a low level andthe avoidance of a magnetically saturated state that can appear in thefront end sections of the magnetic head. Such a magnetic head may have aprofile less prone to the adhesion of dust and other contaminants andcan be manufactured on a mass production basis.

According to one aspect of the invention, there is provided a thin filmmagnetic head comprising:

first and second magnetic pole layers which are made of a thin film of asoft magnetic material and connected to each other at respective basesections thereof;

a thin film coil which in wound around at least one of the firstmagnetic pole layer and the second magnetic pole layer;

a magnetic gap layer which is disposed between a front end section ofthe first magnetic pole layer and a front and section of the secondmagnetic pole layer; and

at least one magnetically insulating layer which is disposed along aplane facing a recording medium, the magnetically insulating layerpartitioning at least one of the front end section of the first magneticpole layer and the frond end section of the second magnetic pole layer.

According to another aspect of the invention, there is provided a methodof fabricating a thin film magnetic head in which a first magnetic polelayer and a second magnetic pole layer are respectively connected tobase sections, a thin film coil is wound at least around one of thefirst magnetic pole layer and the second magnetic pole layer, and amagnetic gap layer is provided between a front end section of the firstmagnetic pole layer and a front end section of the second magnetic polelayer, the method comprising:

a first step of forming the first magnetic pole layer of thin film of asoft magnetic material on a non-magnetic substrate;

a second step of forming the magnetic gap layer and the thin film coilon the first magnetic pole layer;

a third step of forming the second magnetic pole layer of thin film ofsoft magnetic material; and

a fourth step of forming, after the third step, an additional magneticpole layer of thin film of a soft magnetic material over the front endsection of the second magnetic pole layer with a magnetically insulatinglayer interposed therebetween.

The fourth step may instead be a step of forming, between the first stepand the second step, an additional magnetic pole layer of thin film of asoft magnetic material over the front end section of the first magneticpole layer with a magnetically insulating layer interposed therebetween.

In another form, the fourth step may be a step of forming, between thesecond step and the third step, an additional magnetic pole layer ofthin film of a soft magnetic material over the front end section of thesecond magnetic pole layer with a magnetically insulating layerinterposed therebetween.

In still another form, the fourth step may be a step of forming, beforethe first step, an additional magnetic pole layer of thin film of a softmagnetic material under the front end section of the first magnetic polelayer with a magnetically insulating layer interposed therebetween.

In a thin film magnetic head according to the first aspect of theinvention, the front end of at least either the first or second magneticpole layer is divided into a plurality of sub-sections exposed to theplane facing the recording medium by one or more than one magneticallyinsulating layers. Thus, as a result of providing a plurality ofsub-sections in the front end section of at least either of the magneticpole layer, the undershoots in the waveform of the signal reproduced bythe magnetic head attributable to the isolated transition ofmagnetization of the recording medium can be spread over a long periodof time to consequently reduce the amplitude. Additionally, since thefront end sections of the magnetic pole layers do not have to be madeparticularly thin, the generation of a magnetically saturated state inthe magnetic pole layers can be effectively avoided. Still additionally,since the terminals of the front end section of the magnetic pole layersare made flat by providing magnetically insulating layers, dust andother contaminants are effectively prevented from adhering thereto toimprove the reliability of the magnetic head.

With a method of fabricating a thin film magnetic head according to theinvention, there is provided a step of preparing an additional magneticpole layer of a thin film of a soft magnetic material on the front endsection of the second magnetic pole layer with a magnetically insulatinglayer disposed therebetween, and this step is carried out after thecompletion of a known manufacturing process. Since both the magneticallyinsulating layer and the additional magnetic pole layer can be providedduring the process of manufacturing wafers, it can be effectively usedfor mass production.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be apparent from the following description of preferredembodiments of the invention explained with reference to theaccompanying drawings, in which:

FIG. 1A is a schematic cross sectional view of a first known thin filmmagnetic head, and FIG. 1B is a graph showing the output waveform of asignal reproduced by the known thin film magnetic head of FIG. 1A;

FIG. 2A is an enlarged schematic partial sectional view of a secondknown thin film magnetic head, and FIG. 2B is a graph showing the outputwaveform of a signal reproduced by the known thin film magnetic head ofFIG. 2A;

FIG. 3 is a schematic sectional view of a first embodiment of a thinfilm magnetic head according to the invention;

FIG. 4A is an enlarged schematic partial sectional view of the firstembodiment of FIG. 3, and FIG. 4B is a graph showing the output waveformof a signal reproduced by the embodiment of FIG. 3;

FIGS. 5A to 5D are schematic sectional views of a second embodiment of athin film magnetic head according to the invention for use in explainingsequential steps;

FIGS. 6A to 6C are schematic sectional views of a third embodiment of athin film magnetic head according to the invention for use in explainingsequential steps;

FIGS. 7A to 7G are schematic sectional views of a fourth embodiment of athin film magnetic head according to the invention for use in explainingsequential steps;

FIG. 8 is a schematic sectional view of a fifth embodiment of a thinfilm magnetic head according to the invention;

FIG. 9 is a schematic partial sectional view of a sixth embodiment of athin film magnetic head according to the intention; and

FIG. 10 is a schematic partial sectional view of a seventh embodiment ofa thin film magnetic head according to the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

Now, preferred embodiments of the invention are explained with referenceto the drawings.

Firstly, a first embodiment of a thin film magnetic head according tothe invention will be described by referring to FIGS. 3, 4A and 4B, ofwhich FIG. 3 is a schematic sectional view, FIG. 4A is an enlargedpartial sectional view and FIG. 4B to a graph showing the outputwaveform of a signal reproduced by the first embodiment. Here, thecomponents that are same or similar to their counterparts of the thinfilm magnetic head of FIGS. 1A and 1B are denoted respectively by thesame reference symbols and will not be described here any further.

The thin film magnetic head of this embodiment comprises a firstmagnetic pole layer 100 and a second magnetic pole layer 102 that aremade of an alloy of nickel and iron and connected to each other atrespective base sections 100d and 102d, a thin film coil 103 woundaround the second magnetic pole layer 102 and a magnetic gap layer 104disposed between the front end sections 10a and 12a of the first andsecond magnetic pole layers 100 and 102 and made of aluminum oxide. Eachof the front end sections 10a and 12a is divided into two sub-sectionsby a magnetically insulating layer 10c or 12c, and disposed along theplane 12 (FIG. 4A) facing the recording medium. Thus, the front endsection 10a has two tips ie and 10f and the front end section 12a alsohas two tips 12e and 12f (FIG. 4A). The magnetically insulating layer10c and 12c can be produced by any of the known thin film formingtechniques including sputtering, photolithography and dry etching.Therefore, both the first and second magnetic pole layers 100 and 102have a multilayer structure.

As shown in FIG. 4A, the thin film magnetic head of this embodiment hasas many as four front end sub-sections 10e, 10f, 12e and 12f. As aresult the waveform of the signal reproduced by the isolated transitionof magnetization 112 has undershoot outputs 14 that are spread out tobecome flat and make their amplitude almost unrecognizable andnegligible. Additionally, since the front end sections 10a, 12a are notmade thin unlike those of the above described second known thin filmmagnetic head, they are not apt to become magnetically saturated andless prone to the adhesion of dust and other contaminants.

FIGS. 5A to 5D illustrate a second embodiment of a thin film magnetichead according to the invention for use in explaining sequential steps.A method of fabricating a thin film magnetic head according to theinvention will be described hereinafter by way of this second embodimentshown in FIGS. 5A to 5D.

A first magnetic pole layer 20 of nickel-iron alloy is formed on anon-magnetic substrate (not shown) by frame plating. Subsequently, athin copper film coil 22 is formed thereabove with an insulating layerdisposed therebetween, and an organic insulating film 24 is providedthereon to cover the steps formed (FIG. 5A). Thereafter, a magnetic gaplayer 26 of aluminum oxide is formed and an additional magnetic polelayer 28 of nickel-iron alloy is formed on the magnetic gap layer 26 byplating (FIG. 5B). Another thin copper film coil 30 is formed thereabovewith an insulating layer disposed therebetween and, again, anotherorganic insulating layer 32 made of photoresist is formed thereon tocover the steps formed (FIG. 5C). Finally, a magnetically insulatinglayer 34 of aluminum oxide is formed on the additionally magnetic polelayer 28 and a second magnetic pole layer 36 of nickel-iron alloy isformed by frame plating before the resulting structure is cut to apredetermined geometry and lapped (FIG. 5D).

Only an additional magnetic pole layer 28 is formed near the secondmagnetic pole layer 36 in this embodiment of thin film magnetic head.One of the undershoot waveforms that appear on the lateral sides of theisolated transition of magnetization can be reduced with such anarrangement. Because all the steps of the above described method forpreparing a thin film magnetic head can be incorporated into the processof manufacturing wafers, it is particularly suited for mass production,

FIGS. 6A to 6C are schematic sectional views of a third embodiment of athin film magnetic head according to the invention for use in explainingsequential steps. Here, the components of FIGS. 6A to 6C that are sameor similar to their counterparts of the preceding embodiments of thethin film magnetic head are denoted respectively by the same referencesymbols and will not be described here any further.

The thin film magnetic head shown in FIG. 6A is prepared by a knownmethod. Subsequently, a magnetic insulating layer 40 of aluminum oxideis formed on the second magnetic pole layer 102 by means of anappropriate technique such as sputtering, photoresist exposure or ionmilling. Thereafter, an additional magnetic pole layer 42 is formed onthe magnetic insulating layer 40 of nickeliron alloy by plating (FIG.6B). Finally, the resulting structure is cut to a predetermined geometryand lapped (FIG. 6C). This method of fabricating a thin film magnetichead is as effective as the above described method.

FIGS. 7A to 7G are schematic sectional views of a fourth embodiment of athin film magnetic head according to the invention for use in explainingsequential steps.

Firstly, non-magnetic substrate 44 is prepared (FIG. 7A). Subsequently,a recess of a predetermined pattern 46 is produced by means of atechnique involving exposure and development of photoresist and ionmilling at the position for forming an additional magnetic pole layer inthe non-magnetic substrate 44 (FIG. 7B). Then, a nickel-iron alloy layer48a is formed for an additional magnetic pole layer by plating (FIG.7C). Thereafter, unnecessary areas of the nickel-iron alloy layer 48aare removed by plane lapping or etching-back to realize an additionalmagnetic pole layer 48 (FIG. 7D). Then, a magnetically insulating layer50 of oxide aluminum is formed on the non-magnetic substrate 44 exceptpart of the additional magnetic pole layer 48 (FIG. 7E). Subsequently, afirst magnetic pole layer 52 is formed by means of an appropriatetechnique such as plating or sputtering (FIG. 7F). Then, although notshown, a thin film coil, a magnetic gap layer and a second magnetic polelayer are formed along with other necessary components as in the case ofthe preceding embodiments and, finally, the resulting structure is cutto a predetermined geometry and lapped (FIG. 7G). This embodiment andthe method used for fabricating are as effective as their counterpartsdescribed earlier by referring to the second embodiment. In particular,this embodiment is advantageous in that, if an additional magnetic polelayer 48 is formed under the first magnetic pole layer 52 and each layeron the first magnetic pole layer 52 is made flat, the phenomena of thelayers becoming thin at stepped areas can be avoided.

FIG. 8 is a schematic sectional view of a fifth embodiment of a thinfilm magnetic head according to the invention.

This embodiment comprises a first magnetic pole layer 54 and a secondmagnetic pole layer 56 that are made of an nickel-iron alloy andconnected to each other at respective base sections 54a and 56a, a thinfilm coil 103 wound around the second magnetic pole layer 56 and amagnetic gap layer 58 disposed between the front end sections 54b and56b of the first and second magnetic pole layers 54 and 56. A firstadditional magnetic pole layer 54c of nickel-iron alloy is provided atthe front end section 54b and disposed along the plane 60 facing therecording medium, a first magnetically insulating layer 54d of aluminumoxide being disposed between the front end section 54b and theadditional magnetic pole layer 54c. In the same way, a second additionalmagnetic pole layer 56c of nickel-iron alloy is provided at the frontend section 56b and disposed along the plane 60 facing the recordingmedium, a second magnetically insulating layer 56d of aluminum oxidebeing disposed between the front end section 56b and the additionalmagnetic pole layer 56c.

The first additional magnetic pole layer 54c and the first magneticallyinsulating layer 54d are prepared by the method described above byreferring to the fourth embodiment. The second additional magnetic polelayer 56c and the second magnetically insulating layer 56d are preparedby the method described above by referring to the third embodiment.Since this embodiment of the thin film magnetic head comprises a firstadditional magnetic pole layer 54c provided on the first magnetic polelayer 54 and a second additional magnetic pole layer 56c provided on thesecond magnetic pole layer 56, it is as effective as the firstembodiment.

FIG. 9 is a schematic partial sectional view of a sixth embodiment of athin film magnetic head according to the invention. Here, the componentsthat are same or similar to their counterparts of the thin film magnetichead of FIG. 8 are denoted respectively by the same reference symbolsand will not be described here any further.

In this embodiment, a first additional magnetic pole layer 62c is formedunder the front end section 54b of the first magnetic pole layer 54 witha first magnetically insulating layer 62d disposed therebetween, while asecond additional magnetic pole layer 64c is formed over the front endsection 56b of the second magnetic pole layer 56 with a secondmagnetically insulating layer 64d disposed therebetween. However, thefirst additional magnetic pole layer 62c is not held in contact with thefirst magnetic pole layer 54 nor the second additional magnetic polelayer 64c is held in contact with the second magnetic pole layer 56.With such an arrangement, the undershoot waveform of a reproduced signalcan be reduced.

FIG. 10 is a schematic partial sectional view of a seventh embodiment ofa thin film magnetic head according to the invention. Here, thecomponents that are same or similar to their counterparts of the thinfilm magnetic head of FIG. 9 are denoted respectively by the samereference symbols and will not be described here any further.

In this embodiment of thin film magnetic head, a third additionalmagnetic pole layer 62e is formed under the first additional magneticpole layer 62c with a third magnetically insulating layer 62f disposedtherebetween and a fourth additional magnetic pole layer 62g is formedunder the third additional magnetic pole layer 62e with a fourthmagnetically insulating layer 62h disposed therebetween, while a fifthadditional magnetic pole layer 64e is formed over the second additionalmagnetic pole layer 64c with a fifth magnetically insulating layer 64fdisposed therebetween and a sixth additional magnetic pole layer 64g isformed over the fifth additional magnetic pole layer 64e with a sixthmagnetically insulating layer 64h disposed therebetween. With such anarrangement, the undershoot waveform of a reproduced signal can befurther remarkably reduced.

With a thin film magnetic head according to the invention, theundershoot outputs of the waveform of a signal reproduced by themagnetic head that are attributable to the isolated transition ofmagnetization can be spread over a prolonged period of time toconsequently reduce the amplitude of the undershoots since there anincreased number of front end sections are provided for the magneticpole layers. Additionally, since the front end sections of the magneticpole layers do not have to be made particularly thin, the generation ofa magnetically saturated state in the magnetic pole layers can beeffectively avoided. Still additionally since the terminals of the frontend section of the magnetic pole layers are made flat by providingmagnetically insulating layers, dust and other contaminants effectivelyprevented from adhering thereto to improve the reliability of themagnetic head.

With a method of fabricating a thin film magnetic head according to theinvention, the magnetically insulating layers and the additionalmagnetic pole layers can be prepared in the process of manufacturingwafers, it can be effectively used for mass production.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims mar be made without departing from the true scopeof the invention as defined by the claims.

What is claimed is:
 1. A thin film magnetic head comprising:first andsecond magnetic pole layers each made of a thin film of a soft magneticmaterial and connected to each other at respective base sectionsthereof; a thin film coil wound around at least one of said firstmagnetic pole layer and said second magnetic pole layer; a magnetic gaplayer disposed between a front end section of said first magnetic polelayer and a front end section of said second magnetic pole layer; and atleast one magnetically insulating layer having a thickness equal to orthicker than that of said magnetic gap layer, disposed along a planefacing a recording medium, said magnetically insulating layerpartitioning at least one of said front end section of said firstmagnetic pole layer and said front end section of said second magneticpole layer, and said magnetically insulating layer.
 2. A thin filmmagnetic head according to claim 1, in which said at least onemagnetically insulating layer divides at least one of said front endsection of said first magnetic pole layer and said frond end section ofsaid second magnetic pole layer into a plurality of sub-sections.
 3. Athin film magnetic head according to claim 1, which further comprises anadditional magnetic pole layer made of a thin film soft magneticmaterial disposed along said plane facing said recording medium, saidadditional magnetic pole layer being provided over at least one of saidfront end section of said first magnetic pole layer and said front endsection of said second magnetic pole layer with said magneticallyinsulating layer being interposed therebetween.
 4. A thin film magnetichead according to claim 3, in which a plurality of said additionalmagnetic pole layers and a plurality of said magnetically insulatinglayers are alternately provided to form a multilayer structure.